I know they are there to reduce compression but how do I determine whether I need them or not? What I have now is about 1.5mm.
Raf
karmannghia60 ·
Aussieveedubbers · Tech Talk
Shims under barrels
https://forums.aussieveedubbers.com/threads/15414/shims-under-barrels
vw54 ·
Now yr getting into the nitty gritty. Raf you have to work out the compression ratio using a formular. Dont throw them away
Menangler ·
Use this calculator to work out your compression,
http://www.csgnetwork.com/compcalc.html
You will need to know the deck height, the volume of the cylinder head, and of cause the size of your engine.
http://www.csgnetwork.com/compcalc.html
You will need to know the deck height, the volume of the cylinder head, and of cause the size of your engine.
LOWBUG ·
Nice work Dave, what a great sight, everyone should have that in thier favorites
karmannghia60 ·
Thanks. This is for an 1835 so it the following correct?
- bore 92mm
- stroke 69mm (standard)
- head gasket bore 92???
- compressed head gasket thickness (is this the thinkness of the shim?)
- chamber volume (is it 46x46x3.14x69=458.45cc?)
If I use the above with 2mm deck clearance I get compression of 1.97:1 which doesn't sound right. What am I doing wrong?
Raf
- bore 92mm
- stroke 69mm (standard)
- head gasket bore 92???
- compressed head gasket thickness (is this the thinkness of the shim?)
- chamber volume (is it 46x46x3.14x69=458.45cc?)
If I use the above with 2mm deck clearance I get compression of 1.97:1 which doesn't sound right. What am I doing wrong?
Raf
karmannghia60 ·
Ah, and what is a reasonable CR for an daily driver 1835? Around 8.5:1?
lugnuts ·
Dunno bout the rest but chamber volume is measured not calculated and should be something between 40-60cc per chamber.🙂
lugnuts ·
Heres another calculater bit simpler without the H2O bull*hit. http://www.cbperformance.com/enginecalc.html
:thumb
:thumb
Bizarre ·
http://www.aircooled.net/gnrlsite/resource/specgeninfo/calcs.htm
Here is a simpler one
For example
on MY motor
bore 90.5mm
stroke 69mm
deck 2mm
combustion chamber cc's 48
CR = 8.3
To measure the head you need to get it dead flat with the valves in and seated. Then get a syringe and measure the water going in. This will give you your head cc's
Should be around 50-55cc.
Deck height you need to have the cylinders torqued down. Then measure the distance fron the top of the cylinder to the top of the piston.
The new wave of thinking is keeping your deck tight. Cant go too tight our you will bend something.
2mm is good. This "apparently" gives "squish"
If your deck is tight them you need cc's. If you need cc's and the heads have been fly cut then they need opening. Open too far and then you need hemmi-ing.
Is hemi good???
Lets not go there. I actually have hemi cut heads.
I would personally have hemi heads than shims under the barrels and too much deck.
You see where this is going - round and round and round and round
To have an opinion you need to have built several motors and FELT the difference.
Or be like me. I have built one motor (several times) and read heaps and PRETEND i know.
IF you want to be real picky you will measure ALL FOUR cylinders. Not just one
Here is a simpler one
For example
on MY motor
bore 90.5mm
stroke 69mm
deck 2mm
combustion chamber cc's 48
CR = 8.3
To measure the head you need to get it dead flat with the valves in and seated. Then get a syringe and measure the water going in. This will give you your head cc's
Should be around 50-55cc.
Deck height you need to have the cylinders torqued down. Then measure the distance fron the top of the cylinder to the top of the piston.
The new wave of thinking is keeping your deck tight. Cant go too tight our you will bend something.
2mm is good. This "apparently" gives "squish"
If your deck is tight them you need cc's. If you need cc's and the heads have been fly cut then they need opening. Open too far and then you need hemmi-ing.
Is hemi good???
Lets not go there. I actually have hemi cut heads.
I would personally have hemi heads than shims under the barrels and too much deck.
You see where this is going - round and round and round and round
To have an opinion you need to have built several motors and FELT the difference.
Or be like me. I have built one motor (several times) and read heaps and PRETEND i know.
IF you want to be real picky you will measure ALL FOUR cylinders. Not just one
karmannghia60 ·
Thanks a lot. I got plenty to play with and learn by the looks of it